Included in the Cospas Sarsat standard is the requirement that these measurements be made during the application of a thermal shock profile to each individual TCXO. Measurements are taken of not only the frequency response curve of the TCXO over this range, but a further analysis of the characteristics of that curve. The slope of the response must be measured to less than 2 ppb and residual frequency variations cannot exceed 3 ppb while operating within the thermal shock profile.